Apparatus using low spectrum selectively for providing both ADSL and POTS service

ABSTRACT

Asymmetric Digital Subscriber Line (ADSL) data service and Plain Old Telephone Service (POTS) are provided over a subscriber loop by an ADSL transceiver and a control processor located in a local communication center, and a subscriber ADSL modem at the subscriber location. The control processor is responsive to a detection of an origination of a POTS call for generating a first control signal that causes the ADSL transceiver to load ADSL data into tone bins which are only in a frequency band above a predetermined frequency band used for a POTS call for data transmissions over the subscriber loop. The control processor is also responsive to a detection of a termination of a POTS call for generating a second control signal that causes the ADSL transceiver to load ADSL data into tone bins which are in both the predetermined frequency band used for a POTS call and the frequency band thereabove for ADSL data transmissions over the subscriber loop. The subscriber ADSL modem is responsive to third and fourth control signals received from the control processor and multiplexed into the ADSL data transmissions, to load ADSL data into tone bins which are only in a frequency band above a predetermined frequency band used for a POTS call, and load ADSL data into tone bins which are in both the predetermined frequency band used for a POTS call and the frequency band thereabove for ADSL data transmissions over the subscriber loop, respectively.

CROSS REFERENCE TO RELATED APPLICATIONS

This application expressly claims the benefit of earlier filing date andright of priority from the following co-pending patent applications, allof which are assigned to the assignee of the present invention and havethe same inventor: U.S. Provisional Application Serial No. 60/081,116,filed on Apr. 8, 1998, entitled “Use of Low Spectrum Selectively forboth ADSL and POTS”, and U.S. Provisional Application Serial No.60/084,566, filed on May 7, 1998, entitled “Use of Low SpectrumSelectively for both ADSL and POTS in G.Lite”, and to an applicationentitled “Method Using Low Spectrum Selectively For Providing Both ADSLAnd POTS Service” which is being filed concurrently with the presentapplication. Each cited patent application is expressly incorporated inits entirety by reference.

FIELD OF THE INVENTION

The present invention relates to apparatus using low spectrumselectively for both Asymmetric Digital Subscriber Line (ADSL) and PlainOld Telephone Service (POTS) service over a single loop by addingpredetermined control messages to allow rapid mode switching betweenjust ADSL service and combined ADSL and POTS service based on centraloffice or subscriber events indicating voice call initiation.

BACKGROUND OF THE INVENTION

Asymmetric Digital Subscriber Line (ADSL) is defined, and pertinentstandards information thereto is provided, in the Standards DocumentT1E1.4/98-007R1 entitled “Standards Project for Interfaces Relating toCarrier to Customer Connection of Asymmetrical Digital Subscriber Line(ADSL) Equipment”, Sept. 26, 1997, and subsequent revisions edited byBingham and Van der Putten. More particularly, Asymmetric DigitalSubscriber Line (ADSL) has been defined as consisting of a pair ofDiscrete Multitone (DMT) modems, one at each end of a twisted pairsubscriber loop, with band splitters at each end to provide isolationbetween a high frequency spectrum (above 24 KHz) used for datatransmission and lower frequencies (0-4 KHz) used for Plain OldTelephone Service (POTS) or Integrated Services Digital Network (ISDN)used in some applications. These modems use DMT technology to providehigh data bandwidth and the ability to adapt the data rate at startup tomatch the transmission and noise characteristics of each individualsubscriber loop. Each 4.3125 KHz band of the frequency spectrum(referred to as a Tone Bin), with center frequencies from 25.875 KHz(Tone Bin #6) to 1.04 MHz, is populated with a signal which may beconsidered to be a tone whose amplitude and phase are modulated toencode data bits. Tone Bins below 24 KHz (e.g., Tone Bins #1-#5) are notused for data transmissions.

Proposals have been made by various companies to define an alternatespectral assignment for Asymmetric Digital Subscriber Line (ADSL)Discrete Multitone (DMT) modems that allow for the use of lowfrequencies (below 24 KHz) for additional data throughput. In existingclassical ADSL systems, the lower frequencies including the 0-4 KHzvoice band and approximately 20 KHz of guard band thereabove, arereserved for Plain Old Telephone Service (POTS) telephony voice andsignaling transmissions in some applications. In these classical ADSLsystems, the ADSL data transmissions are transmitted in frequency bandsabove 24 KHz (Tone Bin #6 and above) with the different transmissionsseparated by filters in central office and Customer Premises Equipment(CPE) splitters.

Recent interest in “splitterless” ADSL has generated an activity intrying to provide a dual modality for transmissions wherein asubscriber's line could be used either in the classical ADSL mode asdescribed above, or in a data only mode. In the data only mode, thelower frequencies (0-24 KHz) would be used to carry additional DMT“tones” (Tone Bins #1-#5) modulated with additional data. Since thelower frequencies are transmitted preferentially by most telephoneloops, these lower frequencies can add substantial throughput capabilityto the subscriber's line.

The recent focus has been on eliminating the band splitter, at least atthe subscriber premises. This necessitates some reduction in datathroughput, since data carrier amplitudes must be reduced to avoidinterference to POTS voice generated by nonlinearities. Since the POTSphone impedance loads the subscriber loop, it reduces input amplitudeand available spectral bandwidth to the data receivers. Alternatively,POTS filters may be installed on each POTS telephone to prevent the ADSLsignal from reaching, or being adversely affected by, the telephone,whether on-hook or off-hook. Unfortunately, while these POTS filterswill reduce, or substantially eliminate, the POTS signal interferenceand the need to reduce the ADSL signal amplitude, the filters may renderone or two of the tones below Tone #6 unusable. This reduction in databandwidth is viewed as an acceptable tradeoff to reduce the complexityof installation of the service by eliminating equipment rewiring toaccommodate the splitters. Coincidentally, complexity of the modem isreduced due to the narrower bandwidth and the attendant reduced signalprocessing bandwidth.

It is desirable to provide dual modality for transmissions wherein asubscriber's line can be used either in the classical ADSL mode asdescribed above, or in a data only mode while providing rapid modeswitching between just ADSL service and combined ADSL and POTS servicebased on central office or subscriber events indicating voice callinitiation.

SUMMARY OF THE INVENTION

The present invention is directed to apparatus using low spectrumselectively for both Asymmetric Digital Subscriber Line (ADSL) and PlainOld Telephone Service (POTS) service over a single subscriber loop byadding predetermined control messages to allow rapid mode switchingbetween just ADSL service and combined ADSL and POTS service based oncentral office or subscriber events indicating voice call initiation.

Viewed from one aspect, the present invention is directed to apparatusfor providing both Plain Old Telephone Service (POTS) and AsymmetricDigital Subscriber Line (ADSL) data service over a common subscriberloop providing a predetermined frequency spectrum for transmissionpurposes. The ADSL data service makes use of a multiplicity ofquadrature modulated tones separated in frequency from one anotheracross the predetermined frequency spectrum, and POTS makes use of onlya portion of said predetermined frequency spectrum. The apparatuscomprises means for using said portion of the predetermined frequencyspectrum for POTS while a POTS call is in progress, and means forexcluding ADSL data service from at least said portion of thepredetermined frequency spectrum and reducing the number of tones whilea POTS call is in progress, and expanding ADSL data service into saidportion of the predetermined frequency spectrum and increasing thenumber of tones while a POTS call is not in progress.

Viewed from another aspect, the present invention is directed toapparatus for providing bidirectional Asymmetric Digital Subscriber Line(ADSL) data service and Plain Old Telephone Service (POTS) over asubscriber loop. The apparatus comprises an ADSL transceiver and acontrol processor located in a local communication center. The ADSLtransceiver receives ADSL data in a first direction from a remote sourceand loads the received ADSL data into predetermined tone bins fortransmission over the subscriber loop to subscriber data equipment. TheADSL transceiver receives also ADSL data in a second direction in thepredetermined tone bins from the subscriber loop for processing the ADSLdata for transmission to the remote source. The control processor isresponsive to a detection of an origination of a POTS call forgenerating a first control signal that causes the ADSL transceiver toload ADSL data into tone bins which are only in a frequency band above apredetermined frequency band used for a POTS call for data transmissionsover the subscriber loop. The control processor is responsive to adetection of a termination of a POTS call for generating a secondcontrol signal that causes the ADSL transceiver to load ADSL data intotone bins which are in both the predetermined frequency band used for aPOTS call and the frequency band thereabove for data transmissions overthe subscriber loop.

Viewed from still another aspect, the present invention is directed toapparatus for implementing bidirectional Asymmetric Digital SubscriberLine (ADSL) data service and Plain Old Telephone Service (POTS) over asubscriber loop. The apparatus comprises an integrated line circuitwhich comprises detecting and processing circuitry, an ADSL transceiver,and a control processor. The detecting and processing circuitry detectsan origination or termination of a POTS call directed to or from asubscriber coupled to the subscriber loop, and bidirectionally processesthe POTS call for transmission between a remote source and thesubscriber loop. The ADSL transceiver receives ADSL data from a remotesource and loads the received ADSL data into predetermined tone bins forADSL data transmissions over the subscriber loop to subscriber dataequipment. The ADSL transceiver also receives ADSL data from thesubscriber loop in the predetermined tone bins for processing the ADSLdata for data retransmissions to the remote source. The controlprocessor is responsive to a detection of an origination of a POTS callby the detecting and processing circuitry for generating a first controlsignal that causes the ADSL transceiver to load ADSL data into tone binswhich are only in a frequency band above a predetermined frequency bandused for a POTS call for ADSL data transmissions over the subscriberloop. The control processor is also responsive to a detection of atermination of a POTS call by the detecting and processing circuitry forgenerating a second control signal that causes the ADSL transceiver toload ADSL data into tone bins which are in both the predeterminedfrequency band used for a POTS call and the frequency band thereabovefor ADSL data transmissions over the subscriber loop.

The invention will be better understood from the following more detaileddescription taken with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a block diagram of an integrated line card for use in acentral office in accordance with the present invention;

FIG. 2 shows a block diagram of a subscriber modem in accordance withthe present invention;

FIG. 3 is a timing diagram illustrating dual mode switching between aclassical ADSL mode of transmission and a data only mode of transmissionin a subscriber loop as provided by the integrated line card of FIG. 1in accordance with the present invention; and

FIG. 4 is a flow diagram of an exemplary Voiceband Initializationsequence designated in a standards document for ADSL modems.

DETAILED DESCRIPTION

The present invention is directed apparatus for implementing“Splitterless” Asymmetric Digital Subscriber Line (ADSL) service(elimination of band splitters in modems) wherein integrated centraloffice line circuits (ILCs) perform both Plain Old Telephone Service(POTS) and ADSL data service interfaces over a subscriber's loop. Inaccordance with the present invention, a single control entity locatedin the ILC, hereinafter also referred to as an ADSL TerminationUnit-Central Office (ATU-C) modem, has full access to both of the POTSsignaling state and the ADSL data interface. Similarly, an ADSLTermination Unit-Residential (ATU-R) modem is located at the subscriberend of the loop which is a Customer Premises Equipment (CPE) ADSL modemthat has full visibility to analog parameters of the subscriber's loop.The analog parameters can be used to sense the presence of either a POTStelephone in an off-hook state or a reception of a POTS call at thecentral office destined for that POTS telephone.

The present invention takes advantage of the available information(e.g., telephone on-hook or off-hook state, or ringing) to dynamicallyand rapidly modify the ADSL data modem configurations at the centraloffice and the subscriber premises to populate five low tone bins (Tones#1-#5 found in separate frequency bands below 24 KHz) with ADSL dataonly when POTS service is inactive (i.e., telephone is on-hook or nocall is received for termination at that telephone at the centraloffice). The actual tone center frequencies, as defined byT1E1.4/98-007R1 are: Tone Bin 1=4.3125 KHz, Tone Bin 2=8.625 KHz, ToneBin 3=12.9375 KHz, Tone Bin 4=17.25 KHz, and Tone Bin 5=21.5625 KHz.More particularly, the present invention provides the sensing, controllogic, and ADSL inter-modem communication functions necessary to allowdynamic reconfiguration of both the ADSL Termination Unit-Central Office(ATU-C) modem and the ADSL Termination Unit-Residential (ATU-R) modem inresponse to a POTS call that is either initiated by the subscribercoupled to the ATU-R, or received at the central office ATU-C for thatsubscriber from a connected communication system.

Referring now to FIG. 1, there is shown a block diagram of an integratedline card (ILC) 10 (shown within a dashed line rectangle) that islocated, for example, in a central office or local communication center(e.g., a Private Branch Exchange) in accordance with the presentinvention. The ILC 10 generally terminates multiple subscriber loops (ofwhich only subscriber loop 52 is shown), each of which may independentlyrequire either POTS or ADSL service, or both. The integrated line card10 comprises a plurality of ADSL transceivers 12 a-12 n (shown withinseparate dashed line rectangles with only 12 a and 12 n expresslyshown), a Control Processor 14, a Signaling Sense and Control circuits16, a plurality of Digital Signal Processing for Voice and Signalingcircuits 18 a-18 n (shown within separate rectangles with only 18 a and18 n expressly shown), a Time Division MultiplexMultiplexer/Demultiplexer (TDM MUX/DEMUX) circuit 20, a plurality ofadders 22 a-22 n (shown within separate rectangles with only 22 a and 22n expressly shown), a plurality of Digital to Analog Conversion (DAC)circuits 24 a-24 n (shown within separate rectangles with only 24 a and24 n expressly shown), a plurality of Analog to Digital Conversion (ADC)circuits 26 a-26 n (shown within separate rectangles with only 26 a and26 n expressly shown), a plurality of analog front end circuits 28 a-28n (shown within separate rectangles with only 28 a and 28 n expresslyshown) including a corresponding plurality of High Voltage (HV) circuits29 a-29 n (with only 29 a and 29 n expressly shown), a ringing source30, a test access circuit 32, and a loop power feed circuit 34. It is tobe understood that interconnections between elements of the integratedline card 10 are only shown for the associated first elements (e.g., 12a, 18 a, 22 a, 24 a, 26 a, 28 a, and 29 a) of each of the indicatedplurality of n elements for simplicity purposes only, and that each ofthe other corresponding associated n−1 elements are interconnected andfunction in a same manner as is described hereinafter for the associatedfirst elements.

Each of the plurality of ADSL transceivers 12 a-12 n comprises a serialcoupling of a Multiplexer/Demultiplexer (MUX/DEMUX) 40, a Forward ErrorCorrection (FEC) circuit 42, and a Fast Fourier Transform/Inverse FastFourier Transform (FFT/IFFT) circuit 44. The combination of these threeelements 40, 42, and 44 operates on ADSL data bidirectionallypropagating between a data line 57 and an associated subscriber loop(e.g., loop 52). In the ADSL transceiver 12 a, a first (upstream) sideof the MUX/DEMUX 40 is coupled to bidirectionally communicate ADSL dataover data line 57, and Network Timing Reference signals (NTR) over lead58 with an upstream remote source (not shown) of a communication system.The MUX/DEMUX 40 also selectively transmits and receives both a set offunction specific control bits [hereinafter referred to indicator bits(ib)] over lead 54, and control signals indicating an embedded operationchannel (eoc) and an ADSL operations channel (aoc) over lead 56 to andfrom the Control Processor 14. The eoc and aoc channels are transportedacross the subscriber loop 52 as overhead in the multiplex with userdata and indicator bits, and provide a bidirectional communicationchannel between the Control Processors 14 and 114 at the local exchangeand the subscriber premises, respectively. A second (downstream) side ofthe MUX/DEMUX 40 is coupled for bidirectional transmissions to a firstside of the FEC 42. A second side of the FEC 42 is coupled forbidirectional transmissions to a first side of the FFT/IFFT 44. A secondside of the FFT/IFFT 44 is coupled to transmit resulting ADSL datasignals to the adder 22 a, and to receive signals from the subscriberloop 52 via the analog front end circuit 28 a and the ADC circuit 26 a.The ADSL transceiver 12 a also receives control signals from the ControlProcessor 14 via a control bus 59 for selectively controlling allaspects of the ADSL transceiver 12 a such as, for example, populatingand depopulating tone bins with ADSL data.

The ADSL service is realized by a modem which is a combination of thetransceivers 12 a-12 n and control functions provided by the ControlProcessor 14. For data signals received via lead 57, the transceiver(e.g., 12 a), in addition to its modulation functions performed in theMUX/DEMUX 40 on the Data signals on lead 57, combines (a) the modulateduser data stream on lead 57 with (b) two embedded operations channel(eoc) and ADSL operations channel (aoc) messages provided by the controlprocessor 14 over lead 56, (c) Network timing reference signal (NTR) onlead 58, and (d) a set of function specific control bits referred tohereinafter as indicator bit 18 (ib 18) on lead 54 which is the bitnumber in an ADSL data signal transmitted over the subscriber loop(e.g., 52). These combined signals are used subsequently to create theanalog signal for the high-frequency spectrum used for ADSL transmissionon the loop 52. It is to be understood that in future implementations, asingle Digital Signal Processor (DSP) (not shown) may perform the modemfunction (shown as performed by the ADSL Transceivers 12 a-12 n and theControl Processor 14) for multiple subscriber loops.

In operation, the MUX portion of the MUX/DEMUX 40 in the ADSLTransceiver 12 a combines the various components of a single compositeADSL line signal received on leads 54, 56, 57 and 58 for transmission inthe downstream direction to the subscriber loop 52, while the DEMUXportion separates the demodulated ADSL line signal to form the variouscomponents for transmission on leads 54, 56, 57, and 58 in the upstreamdirection from the subscriber loop 52. The FEC 42 performs the encodingand decoding forward-acting error correcting of the data bit streamsreceived from the MUX 40 in the downstream direction and from theassociated ADC 26a in the upstream direction. In the FFT/IFFT 44, theADSL data signals are constructed by Inverse Fourier Transformtechniques based on control signals from the Control Processor 14 viathe control bus 59. Therefore, the composite digital ADSL data signalsreceived by the transceiver 12 a from the upstream remote source (notshown) via lead 57 are forward error corrected, then decomposed, and thebits are assigned to tone bins and encoded to a discrete multitonesymbol by the IFFT portion of the FFT/IFFT 44 under control signals fromthe Control Processor 14 via the control bus 59. In the reversedirection, the ADSL data signals from the subscriber loop 52 areconverted into a digital data signal by the FFT portion of the FFT/IFFT44 before being forward error corrected in the FEC 42 and thendemultiplexed in the MUX/DEMUX 40 to separate the user and control datastreams onto their proper leads 54, 56, 57, and 58.

In the ILC 10, POTS service is provided between a Pulse Code Modulation(PCM) Link 50 and each of the associated subscriber loops (e.g., loop52). For POTS service to multiple subscriber loops, the ILC 10 uses theTime Division Multiplex Multiplexer/Demultiplexer (TDM MUX/DEMUX)circuit 20, the plurality of Digital Signal Processing for Voice andSignaling circuits 18 a-18 n, and the Signaling Sense and Controlcircuit 16. The PCM Link 50 is coupled to the TDM MUX/DEMUX circuit 20,and the TDM MUX/DEMUX circuit 20 is coupled to the plurality of DigitalSignal Processing for Voice and Signaling Circuits 18 a-18 n, and to theSignaling Sense and Control circuit 16. Each of the plurality of DigitalSignal Processing for Voice and Signaling Circuits 18 a-18 n is coupledto the Control Processor 14, the Signaling Sense and Control circuits16, a corresponding one of the plurality of adders 22 a-22 n fortransmitting POTS calls to the associated subscriber loop (e.g. loop52), and a corresponding one of the plurality of ADC circuits 26 a-26 nfor receiving POTS calls and signaling messages from the associatedsubscriber loop.

For POTS operation, the TDM MUX/DEMUX circuit 20 receives PCM channelsignals and channel associated signaling bits from the PCM link 50, anddemultiplexes the PCM channel signals for an associated subscriber loop(e.g., loop 52). The demultiplexed PCM channel signals are transmittedto the associated one of the Digital Signal Processing for Voice andSignaling circuits 18 a-18 n. The associated signaling bits aretransmitted to the Signaling Sense and Control circuit 16 via lead 61where they are stored for use by the Control Processor 14 to initiatesubscriber loop events such as ringing, etc. In the reverse direction,the TDM MUX/DEMUX circuit 20 receives the PCM channel signals from theplurality of the Digital Signal Processing for Voice and Signalingcircuits 18 a-18 n provided by the associated subscriber loop (e.g.,loop 52), and time division multiplexes the PCM channel signals intotheir proper time slots for transmission on the PCM link 50 to theupstream remote source (not shown). The Digital Signal Processing forVoice and Signaling circuits 18 a-18 n provides anti-alias filtering,code law computation, gain adjustment, hybrid impedance match, ringinggeneration, loop state detection, and other analog-loop relatedfunctions by performing computations on the digital representation ofthe subscriber loop signals flowing in both directions. Detectedsubscriber loop signaling state information is passed to the SignalingSense and Control circuit 16, and in the reverse direction transmittedloop state information is received from the Signaling Sense and Controlcircuit 16. In some implementations, where necessary, the Digital SignalProcessing for Voice and Signaling circuits 18 a-18 n may also performadditional digital filtering functions. In a fully integratedimplementation, the digital filtering functions will be performed by thesame Digital Signal Processing for Voice and Signaling circuit (e.g., 18a) that performs the ADSL transceiver functions, and will includePOTS/ADSL band separation filters (not shown).

The Control Processor 14 controls all aspects of both the ADSL and POTSoperations for multiple subscriber loops (e.g., loop 52). The ControlProcessor 14 receives status signals from, and transmits control signalsto, both of the ADSL transceivers 12 a-12 n and the POTS Digital SignalProcessing for Voice and Signaling circuits 18 a-18 n via the SignalingSense and Control circuit 16. The Control Processor 14 also monitorsADSL transmissions and adjusts bit loading via control signals on lead59, and transmits levels in response to detected variations in the ADSLline transport capacity via control signals on lead 59. Still further,the Control Processor maintains the status of ADSL line maintenanceinformation blocks (MIBs) and communicates with the associated ATU-R atopposite end of the associated subscriber's loop via the eoc, aoc, andib signals sent to the ADSL transceiver (e.g., 12 a) associated withthat ATU-R via lines 54 and 56. The Control Processor 14 furtherbidirectionally communicates with data network management entities atthe upstream remote source (not shown) via a signaling message channel55. The Control Processor 14 also interprets received POTS subscriberloop signaling states (on-hook, off-hook), sets POTS loop states(ringing, current feed, etc.), and controls loop test access via controlmessages sent over lead 53. These control messages are based oncommunications had with a POTS switch (not shown) at the upstream remotesource via the signaling message channel 55 or via channel associated(CAS) signaling bits carried in the PCM time slots for each channel asreceived via PCM link 50 and directed to the Signaling Sense and Controlcircuit 16 via lead 61. The above described functioning of the ControlProcessor 14, with respect to ADSL, comprises standard functions assuggested in the ADSL Standards Document T1E1.4/98-007R1 entitled“Standards Project for Interfaces Relating to Carrier to CustomerConnection of Asymmetrical Digital Subscriber Line (ADSL)Equipment”—T1.413 Issue 2, Sep. 26, 1997, and subsequent revisionsedited by Bingham and Van der Putten. The above-described functioning ofthe Control Processor 14 with respect to POTS is considered prior art aswould be found in existing line controllers of TDM digital switchingequipment as found in, for example, Siemens EWSD and DCO linecontrollers.

The present invention adds a new function to the Control Processor 14 tocouple the detection of POTS subscriber loop on-hook and off-hook statechanges to accordingly populate (for the on-hook state) and depopulate(for the off-hook state) the tones #1-#5 in the 0-24 KHz frequency bandbetween the subscriber's ATU-R modem (shown in FIG. 2) and theassociated ADSL transceiver (e.g., 12 a). In operation, the ControlProcessor 14 receives a control signal via the Digital Signal Processingfor Voice and Signaling circuits 18 a-18 n and the Signaling Sense andControl circuit 16 indicating any change in the hook state of theassociated subscriber loop, and in response to a change in hook state tosend an appropriate hook state control signal (logical 0 or 1) inindicator bit 18 (ib 18) to the associated ATU-R at the subscriber'send. Concurrent therewith, the Control Processor 14 adjusts both the bitloading and the transmit amplitude of the tones #1-#5, and the resultingdata mapping to transport additional data bits in the additional 0-24KHz bandwidth, via control signals on the control bus 59.

Each of the plurality of Adders 22 a-22 n receives (a) the processedADSL data signals (tones 1-up or tones 6-up, depending one whether theassociated subscriber is on-hook or off-hook, respectively) from theassociated one of the ADSL transceivers 12 a-12 n, and (b) the processedPOTS signals from the associated one of the Digital Signal Processingfor Voice and Signaling circuits 18 a-18 n, and adds the two signals toform a combined subscriber output signal. Each of the adders 22 a-22 ntransmits the combined subscriber output signal to the one of theplurality of DACs 24 a-24 n associated with that subscriber. Whileadders 22 a-22 n are shown in FIG. 1 as separate adders for eachsubscriber loop, highly integrated implementations can be made toperform this function in a common Digital Signal Processing for Voiceand Signaling circuit (e.g., 18 a) which may additionally be shared overmultiple subscriber loops. Each of the DACs 24 a-24 n converts thereceived digital combined subscriber output signal into a correspondinganalog subscriber output signal for transmission to the correspondingone of the plurality of analog front end circuits 28 a-28 n associatedwith that subscriber.

Each of the plurality of analog front end circuits 28 a-28 n providesfor gain and impedance matching for transmitting the analog combinedsubscriber output signal on the associated subscriber loop (e.g., 52) ina downstream direction, and for reception of a combined subscribersignal from the associated subscriber loop (e.g., 52) in an upstreamdirection. Each of the High Voltage sections 29 a 29 n, forming part ofa corresponding one of the plurality of analog front end circuits 28a-28 n, isolates the associated analog front end circuit 28 from highvoltages used for ringing and loop power feed as provided by the Ringingsource 30 and the Loop Power Feed 34, respectively. More particularly,the Ringing source 30 provides a ringing signal to the subscriber when aPOTS call is directed to the subscriber (when the subscriber is thecalled party). Alternatively, in balanced ringing applications, theringing signal may be generated by the corresponding Digital SignalProcessor for Voice and Signaling circuit 18 a-18 n, and carried throughthe same path as the voice signals. The Test Access 32 provides metallicswitching to connect the subscriber loop (e.g., loop 52) to a remotetest console (not shown) where a technician supervises testing for loopfailures. The Loop Power Feed 34 provides a connection to the centraloffice battery (not shown) to power the subscriber loop (e.g., loop 52).This power is used both to power telephone sets and to enable loopcurrent flow as a means of the detection of the hook state.

Referring now to FIG. 2, there is shown a block diagram of a AsymmetricDigital Subscriber Line (ADSL) Termination Unit-Residential (ATU-R)modem 100 (shown within a dashed-line rectangle) and a telephone 102together with an optional low pass filter 103 (shown within a dashedline rectangle) that are coupled to a subscriber loop 52 in accordancewith the present invention. The modem 100 comprises an ADSL transceiver112 (shown within a dashed-line rectangle), a Control Processor 114, aDigital to Analog Conversion (DAC) circuit 124, an Analog to DigitalConversion (ADC) circuit 126, and an analog front end circuit 128. TheADSL transceiver 112 comprises a serial coupling of aMultiplexer/Demultiplexer (MUX/DEMUX) 140, a Forward Error Correction(FEC) circuit 142, and an Fast Fourier Transform/Inverse Fast FourierTransform (FFT/IFFT) circuit 144 between a subscriber's data line 150,which is coupled to a subscriber data terminal (not shown), and theassociated subscriber loop 52. The combination of circuits 140, 142, and144 operates on the ADSL data propagating to or from the associatedsubscriber loop 52. It is to be understood that the elements 112, 114,124, 126, 128, 140, 142, and 144 operate on ADSL data in a similarmanner to that described hereinbefore for the elements 12, 14, 24, 26,28, 40, 42, and 44 in the Integrated central office Line Circuit (ILC)10 of FIG. 1. A telephone 102, or other communication device used by thesubscriber for POTS calls is coupled to the subscriber loop 52. Alsoshown is an optional low pass filter 103, which may be required in someapplications for optimum functioning of the ADSL and POTS services. Thelow pass filter 103 isolates the subscriber loop 52 from both loadingand possible nonlinear responses due to some POTS telephones, thusimproving the throughput and channel robustness for the ADSL modems 100.Both low pass filter 103 and distributed splitters are suggested forthis function in the ADSL literature, and both enhance the operation ofthe present invention by insuring that the control messages forinsertion and removal of data in the low tones flow without interruptionof the ADSL transmission. If the distributed configuration is used, thehigh-pass input filter characteristic of the analog front end 128 at theATU-R must be dynamically modified to pass the low tones when they areused for data.

In operation, the MUX portion of the MUX/DEMUX 140 combines the varioussignal components received on leads 150, 154, 156, and 159 forgenerating a single composite ADSL line output signal for subsequenttransmission on the subscriber loop 52. The DEMUX portion separates thedemodulated ADSL line signal received from the subscriber loop 52 toform the various signal components for transmission on leads 150, 154,156, and 159. An indicator bit (e.g., ib 18) for propagation on lead 154is one of these components. The FEC 142 performs the encoding anddecoding forward-acting error correcting of the data bit streamsreceived from the MUX 140 and the ADC 126, respectively, of theassociated data channel in the transceiver 112. In the FFT/IFFT 144, theADSL data signals are constructed by Inverse Fourier Transformtechniques. Therefore, the composite digital ADSL data signals receivedfrom the subscriber over lead 150 by the transceiver 112 is forwarderror corrected, then decomposed, and the bits are assigned to tone binsand encoded into a discrete multitone symbol by the IFFT portion of theFFT/IFFT 144 prior to being converted to an analog data signal in theDigital to Analog Conversion (ADC) circuit 126. In the reversedirection, the ADSL data signal from the subscriber loop 52 is convertedinto a digital data signal by the FFT portion of the FFT/IFFT 144 beforebeing forward error corrected in the FEC 142 and then demultiplexed toseparate the user and control data streams onto their proper leads 150,154, 156, and 159. The DAC 124 converts the received digitalsubscriber's data signal into a corresponding analog signal fortransmission to the analog front end circuit 128.

The analog front end circuit 128 provides for gain and impedancematching for transmitting the analog subscriber's data signal from theDAC 124 onto the associated subscriber loop 52, and for reception of asubscriber destined analog data signal from the associated subscriberloop 52. In an alternative implementation, the ADSL transceiver 100 mayalso include an optional Ringing and DC Level Detector 116 (shown withina dashed line rectangle) to analyze the DC and very low frequencyspectrum of the received subscriber loop 52 signal, provided from theFFT 144 function via lead 162, to detect both ringing (normally at 25 or50 Hz) and changes in the loop DC voltage drop due to current flowthrough the hookswitch of the POTS telephone 102. This providesautonomous detection, at the subscriber end of the loop 52, of theorigination and termination of POTS calls. This combined detection maybe used to signal POTS loop state changes to the Control Processor 114on lead 161 in lieu of the hereinbefore defined signals received fromthe ATU-C of FIG. 1 via the ADSL composite signal and presented to theControl Processor 114 on leads 154 and/or 156. In this alternativeimplementation, precise time synchronization of events between the ATU-Cand the ATU-R is provided by counting the Discrete Multitone (DMT)symbols flowing on the ADSL spectrum of the subscriber loop 52.

As was indicated hereinbefore, in the ILC 10 of FIG. 1, the ControlProcessor 14 receives the subscriber's loop hook state changes from theassociated Digital Signal Processing for Voice and Signaling circuits 18a-18 n via the Signaling Sense and Control circuit 16. The ControlProcessor 14 then sends an appropriate hook state message on indicatorbit 18 (ib 18), or via an aoc message, to the associated ATU-R modem 100(ATU-R) at the subscriber's end. The modem 100 of FIG. 2 receives suchappropriate state of the indicator bit 18 or the aoc message, and thedemultiplexer portion of the MUX/DEMUX 140 directs such indicator bit 18via lead 154, or the aoc message via lead 156, to the control processor114. The Control Processor 114 in the ATU-R modem 100 receives the hookstate message from the MUX/DEMUX 140 via lead 154 or 156, and adjustsboth the bit loading and the transmit amplitude of the tones #1-#5 andthe resulting data mapping via a control bus 159 in order to transportadditional data bits in the tone bins #1-#5 in the 0-24 KHz bandwidth.More particularly, the Control Processor 114 uses the detection ofon-hook and off-hook state changes of the telephone 102 and the POTSsubscriber loop 52 as indicated in the indicator bit 18 or the aocmessage, to accordingly populate (for the on-hook state) and depopulate(for the off-hook state) user data to or from the subscriber's remotedata terminal (not shown) which is connected to lead 150 to the tones#1-#5 in the 0-24 KHz frequency band from or to the associated ADSLtransceiver (e.g., 12 a) in the ILC 10 of FIG. 1.

For example, when the indicator bit 18 is used to contain the ATU-Csensed loop state at the ILC 10 of FIG. 1, then no energy will betransmitted in the low tone bins #1-#5 (the tone bins are depopulated)when the indicator bit is set to a logical “1”, and the population ofthe low tone bins #1-#5 with data is enabled when the indicator bit isset to a logical “0”. Similarly, if aoc hook state messages are used, anexemplary ⅗-majority vote on five separate repetitions of the message isrecommended for detection of the POTS idle (on-hook) state to result inthe population of data in tone bins #1-#5. Still further, an exemplary⅔-majority vote should occur for the POTS-busy (off-hook) statedetection and removal of data in the tone bins #1-#5. Such asymmetricdetection voting favors protection of the POTS service over datacapacity since robust operation without false transitions betweenservices is assured. It is to be understood that any suitable logicalvalues for the indicator bit (ib 18), or the majority vote values forproviding the appropriate aoc hook state messages, can be used. However,it is preferable to use the indicator bit hook state message techniquesince the allowed time to remove tones from the voiceband (0-24 KHz) islimited, and there is always a possibility of a queue of aoc and eocmessages which could extend the response time to an unacceptable timeperiod. In the aforementioned alternative implementation, the ATU-Rautonomously populates and depopulates the aforementioned tone bins #1to #5 in a similar manner based on locally detected state changes, andtransmits an aoc message to the ATU-C indicating the time of change intone use. Concurrently, the ATU-C populates and depopulates theaforementioned tone bins based on its own locally detected subscriberloop state information, as described hereinbefore, and transmits an aocmessage indicating the time of change in tone use. Upon receipt of suchaoc message, each unit (ATU-C and ATU-R) updates its receiver profile toaccommodate the changed spectrum use.

Referring now to FIG. 3, there is shown a timing diagram illustratingdual mode switching between a classical Asymmetric Digital SubscriberLine (ADSL) and Plain Old Telephone Service (POTS) mode of transmissionand an ADSL data only mode of transmission in a subscriber loop asprovided by the Integrated Line Card (ILC) 10 of FIG. 1 in accordancewith the present invention. The timing diagram illustrates call stateactivities 200, 202, 204, 206, and 208 versus time, and related messagechannel signals along axis 210, ringing signal activity along axis 220,hook state (on-hook, off-hook) activity along axis 230, ADSL messageactivity along axis 240, and the use activity of tones #1-#5 in the 0-24KHz frequency band along axis 250 for each of the call states. Duringthe idle call state 200, the hook state of the subscriber's telephone102 (shown in FIG. 2) is shown as on-hook along axis 230, and the tones#1-#5 are in use with ADSL digital data as shown along axis 250. When anincoming call is indicated for termination at the subscriber's telephone102 (the called party), an incoming call message channel signal 212 isreceived over the signal message channel 55 by the Control Processor 14in the ILC 10 of FIG. 1. The Control Processor 14 transmits an ADSL“depopulate” message 242 via either indicator bit 18 or an aoc messagesignal to depopulate ADSL data being transmitted via the tones #1-#5 inthe ADSL transceiver (e.g., 21 a in FIG. 1) and in the ATU-R modem 100(shown in FIG. 2). The ADSL data transmissions are shown as beingdepopulated at point 252 at or just before transmission of ringingsignals 222 from the ringing source 30 (shown in FIG. 1) to thesubscriber's telephone 102 (shown in FIG. 2) over the subscriber loop 52(shown in FIGS. 1 and 2).

In response to the ringing signals 222, the subscriber picks up thetelephone receiver and the telephone 102 goes off-hook at point 232 tocomplete the POTS call. When the call is concluded, the subscriber hangsup the telephone receiver at point 234, and an on-hook state occurs. Theon-hook state is detected at the Signaling Sense and Control circuit 16in FIG. 1, and a disconnect signal 214 is sent by the Control Processor14 (shown in FIG. 1) via the signaling message channel 55 to the remotesource in order to free this call from the remote source (not shown).The Control Processor 14 also sends a “populate” signal 244 via theindicator bit 18 or an aoc message to cause both the ADSL transceiver(e.g., 12 a in FIG. 1) and the ATU-R modem 100 (shown in FIG. 2)associated with the subscriber's telephone 102 to again populate thetones #1-#5 with data at point 254.

When the subscriber originates a POTS call during a period 206, thetelephone 102 goes to the off-hook state at point 236. The SignalingSense and Control circuit 16 in FIG. 1 detects such off-hook state andinforms the Control Processor 14 of FIG. 1 of such hook state change.The Control Processor 14 transmits both an originating call signal 216via the signal message channel 55 to the remote source location, and a“depopulate” ADSL message signal 246 to the ADSL transceiver (e.g., 12a) and the ATU-R modem 100 of FIG. 2 associated with the subscriberoriginating the POTS call. At point 256 the tones #1-#5 are depopulatedfrom carrying ADSL data and are available for the POTS call. Once thesubscriber goes back on-hook at point 238 at the end of the POTS call anidle state 208 occurs, and the Signaling Sense and Control circuit 16 inFIG. 1 detects such on-hook state and informs the Control Processor 14of FIG. 1 of such hook state change. The Control Processor 14 then sendsboth a “remote disconnect” signal 218 to the remote source location vialead 55, and a “populate” signal 248 to the ADSL transceiver (e.g., 12a) and the ATU-R modem 100 of FIG. 2 associated with the subscriber. Atpoint 258 the tones #1-#5 are again populated with ADSL data.

Referring now to FIG. 4, there is shown a flow diagram of exemplaryextensions to the known ADSL Initialization as is described in Section 9of T1E1.4/98-007R1 (cited hereinbefore) for ADSL modems which definesand provides details of such sequence information exchange. TheVoiceband Initialization sequence extensions indicates steps taken ateach of an ADSL Termination Unit-Central Office (ATU-C) modem (e.g., 12a and 14 shown in FIG. 1) forming part of the Integrated central officeLine Circuits (ILC) 10 shown in FIG. 1, and an ADSL TerminationUnit-Residential (ATU-R) modem 100 shown in FIG. 2. The VoicebandInitialization sequence includes both negotiation of voiceband tonecapability and analysis of the low frequency spectrum (0-24 KHz) to settone amplitude and data loading in the ATU-C and ATU-R. During thissequence, the high frequency spectrum (above 24 KHz) is used for normalADSL data transmissions.

During a first interval 300, both the Control Processor 14 (shown inFIG. 1) and the Control Processor 114 (shown in FIG. 2) in the ATU-C andATU-R, respectively, may perform handshake using a modulation basedprotocol exchange of predetermined initialization data. In interval 302,both the Control Processor 14 and the Control Processor 114 in the ATU-Cand ATU-R, respectively, perform measurements of the loop transmissioncharacteristics in the ADSL spectrum, as described in T1E1.4/98-007R1and exchange functional parameters from the measurements that were made.During time period 320, the control processors 14 and 114 simultaneouslyperform both normal ADSL data exchange in the frequency band above 24KHz and the extended initialization required for use of the frequencyband below 24 KHz, as is shown in intervals 304, 306, 308, 310, 312,314, and 316. During the intervals 304, 306, and 308, state transitionson the ib18 indicator bit are used to “advertise” the ATU's capabilityto support the use of the low spectrum. Upon detection of these statetransitions, the ATU-R then waits for the ib18 information bit toindicate the idle state of the subscriber loop, and then transmits acomposite signal, designated R-VB-REVERB, in all tones #1 through #5 ininterval 312. Detection of this signal at the ATU-C provides both aconfirmation of the ATU-R's capability to support the use of the lowspectrum, and an opportunity to measure the transmission loss of the lowspectrum channel on the subscriber loop. After analyzing the receivedsignal, the ATU-C then sends the C-VB-B&G message in the aoc signal tothe ATU-R in interval 314. The ATU-C uses this information to update itsreceiver profiles. In interval 316, both units (ATU-C and ATU-R) mayoptionally send a VB-Seque signal in the low spectrum. This signal wouldallow precise synchronization of the beginning of actual data flow usingthe added low spectrum capacity. Alternatively, the data flow could bemade to begin a known time interval after the beginning of theR-VB-REVERB signal. During interval 320, a “Showtime” state is carriedout where ADSL data is transmitted in tone bins #6 and up (above 25 KHz)between the ATU-C and ATU-R. “Showtime” is an operating state of a pairof ADSL modems, and is defined in the ADSL Standards DocumentT1E1.4/98-007R1 entitled “Standards Project for Interfaces Relating toCarrier to Customer Connection of Asymmetrical Digital Subscriber Line(ADSL) Equipment”—T1.413 Issue 2, Sep. 26, 1997, and subsequentrevisions edited by Bingham and Van der Putten.

More particularly, in interval 304, the Control Processor 14 in theATU-C sets the indicator bit 18 (ib 18) to a logical “1” which isnormally sent to the associated ADSL transceiver (e.g., 12 a shown inFIG. 1) on lead 54. Nothing occurs at the ATU-R during interval 304. Ininterval 306, the Control Processor 14 in the ATU-C sets the indicatorbit 18 (ib 18) to a logical “0”. Nothing occurs at the ATU-R duringinterval 306. In interval 308, the Control Processor 14 in the ATU-Cagain sets the indicator bit 18 (ib 18) to a logical “1” and sends thissignal over the subscriber loop 52 to the Control Processor 114 in theATU-R in an ADSL composite signal. Upon reception of the logical “1”signal in “ib 18”, the Control Processor 114 in the ATU-R performs adetection of the ATU-C's resulting voiceband (VB) capability. Ininterval 310, the Control Processor in the ATU-C may, if the POTS stateis busy, set the indicator bit 18 to define a Plain Old TelephoneService (POTS) busy state where the subscriber telephone 102 (shown inFIG. 2) is off-hook or a call is incoming to the telephone 102. Ininterval 311, the Control Processor transmits the POTS state (IDLE)wherein the indicator bit 18 is equal to a logical zero (ib 18=0) anddefines the on-hook state, and transmits this signal to the ControlProcessor 114 in the ATU-C which is awaiting the signal for defining theIdle (on-hook) state (Wait for idle). In interval 312, the ControlProcessor 114 in the ATU-R transmits a Residence-VoiceBand-Reverberation (R-VB-REVERB) signal, which is a defined signal andis shown capitalized, and transmits this signal via the subscriber loop52 to the Control Processor 14 in the ATU-C. The R-VB-REVERB signal isdefined as the extension to the 0-24 KHz spectrum of the normalR-REVERB-3,4,5 tones defined in T1E1.4/98-007R1 (cited hereinbefore).The R-VB-REVERB signal is a wideband pseudo-random signal used forestimation of the upstream Signal-To Noise Ratio (SNR) at the ATU-C.More particularly, this signal is defined herein as an arbitrarypseudo-random 12-bit sequence, 101000010010 applied in pairs as d_(n),d_(n+1) coefficients to the DC, Nyquist, and succeeding tone binsthrough d₁₀, d₁₁ applied to tone #5. The amplitude of each carrier isset to produce a spectral density of −38 dBm. Tones above the lowspectrum carry user data during this interval. Note that any otherpseudo-random sequence transmitted at known amplitude would worksimilarly. The Central Office Control Processor 14 performs a VoiceBand-Analysis (C-VB-Analysis) which analyzes the voice band channel(0-24 KHz).

The analysis process produces a measurement of the signal amplitude andchannel noise for each tone channel, which is then used by the ControlProcessor 14 to compute, for each tone channel, the optimum transmissionamplitude. In interval 314, the Control Processor 14 in the ATU-Cencodes and transmits this information to the ATU-R over the aocchannel, using a suitable encoding. An example encoding is an orderedsequence of 6 byte pairs wherein the first 4 bits of the first byte of apair represent the bits to be encoded into that tone, b_(I), and theremaining 12 bits represent the relative gain of that tone, g_(i). Eachb_(I) shall be represented as an unsigned 4-bit integer, with validb_(I)s lying in the range of zero to the maximum number of bits that theATU-R is prepared to modulate onto any sub-carrier. Each g_(i) shall berepresented as an unsigned 12-bit fixed-point quantity, with the binarypoint assumed just to the right of the third most significant bit. Forexample, a g_(i) with binary representation (most significant bit listedfirst) of 001,010000000 would instruct the ATU-R to scale theconstellation for carrier i, by a factor of 1.25, so that the power inthat carrier shall be 1.94 dB higher than it was during R-VB-REVERB. Theabove encoding is modeled after the encoding suggested in the ADSLStandards Document T1E1.4/98-007R1 entitled “Standards Project forInterfaces Relating to Carrier to Customer Connection of AsymmetricalDigital Subscriber Line (ADSL) Equipment”—T1.413, Issue 2, Sep. 26,1997, and subsequent revisions edited by Bingham and Van der Putten,with the exception that the encoded information is transmitted via theaoc channel rather than via a data message specific to the bits andgains function. The Bits and Gains measurement is a measurement of thechannel to determine how many bits can be placed in each tone bin, andis considered as core information for populating tone bins.

In interval 314, the Control Processor 114 in the ATU-R performs avoiceband profile update (R-VB-Profile Update) based on information ofchannel measurements of a telephone on-hook voice channel received fromthe ATU-C, and stores a list of channel measurements in a profile table.More particularly, once the voice channel has been measured in theupstream direction at the Control Processor 14 in the ATU-C, ADSLoperating channel (aoc) messages are transmitted in the downstreamdirection to the ATU-R by the Control Processor 14. The informationstored in the profile table is based on these aoc messages. In interval316, each of the ATU-C and ATU-R transmit a defined Segue signal(VB-SEGUE?) which is a broadband signal across the low tones #1-#5 thatare going to be used. The Segue signal is the signal that causes achange from performing the Voiceband Initialization sequence to a“Showtime” state. The “Showtime” state is the operating state of a pairof ADSL modems (ATU-C and ATU-R), and is defined in the T1.413 and ITUstandard cited hereinbefore. The Voiceband Initialization sequenceprovides a definition of a mandatory “pulse” on the ATU-C indicator bit#18 at the beginning of the Showtime state, and allows the ATU-R to knowthe state of the current POTS service.

In accordance with the present invention, the Control Processor 14 ofFIG. 1 includes any suitable program (e.g., with a Look-Up Table) whichwill provide a first control message on lead 59 to the appropriate ADSLtransceiver (e.g., 21 a) to cause the FFT/IFFT 44 therein to populatetone bins #1-#5 in the 0-24 KHz frequency band during periods when noPOTS service is occurring on an associated subscriber loop (e.g., 52).Still further, the suitable program in the Control Processor 14 wouldprovide a second control message on lead 59 that causes the FFT/IFFT 44to depopulate tone bins #1-#5 in the 0-24 KHz frequency band duringperiods when POTS service is occurring on the associated subscriber loop(e.g., 52). Additionally, the Control Processor 14 transmits a firstcontrol signal on either one of indicator bit #18 (logical 1 or 0) vialead 54, or an aoc message via lead 56, that causes the ATU-R modem 100shown in FIG. 2 at the remote end of the subscriber loop 52 to populatethe tone bins #1-#5 when POTS service is occurring on the associatedsubscriber loop 52. Alternatively, the Control Processor 14 transmits asecond control signal on either one of indicator bit #18 (logical 0or 1) via lead 54, or an aoc message via lead 56, that causes the ATU-Rmodem 100 shown in FIG. 2 at the remote end of the subscriber loop 52 todepopulate the tone bins #1-#5 when POTS service is occurring on theassociated subscriber loop 52. The Control Processor 14 provides suchabove-mentioned control signals in response to control signals from theSignaling Sense and Control circuit 16 or the Signal Message Channel 55indicating a change in the state of the POTS service to a predeterminedsubscriber.

It is to be appreciated and understood that the specific embodiments ofthe present invention described hereinabove are merely illustrative ofthe general principles of the invention. Various modifications may bemade by those skilled in the art which are consistent with theprinciples set forth.

What is claimed is:
 1. An apparatus for providing bidirectionalAsymmetric Digital Subscriber Line (ADSL) data service and Plain OldTelephone Service (POTS) over a subscriber loop, comprising: an ADSLtransceiver located in a local communication center for receiving ADSLdata in a first direction from a remote source and loading the receivedADSL data into predetermined tone bins for transmission over thesubscriber loop to subscriber data equipment, and for receiving ADSLdata in a second direction in the predetermined tone bins from thesubscriber loop for processing the ADSL data for transmission to theremote source; and a control processor responsive to a detection of anorigination of a POTS call for generating a first control signal thatcauses the ADSL transceiver to load ADSL data into tone bins which areonly in a frequency band above a predetermined frequency band used for aPOTS call for data transmissions over the subscriber loop, andresponsive to a detection of a termination of a POTS call for generatinga second control signal that causes the ADSL transceiver to load ADSLdata into tone bins which are in both the predetermined frequency bandused for a POTS call and the frequency band thereabove for datatransmissions over the subscriber loop, wherein the ADSL transceivercomprises a Fast Fourier Transform/Inverse Fast Fourier Transform(FFT/IFFT) circuit wherein the IFFT circuit is responsive to the firstcontrol signal from the control processor for loading ADSL data into thetone bins in the frequency band above the predetermined frequency bandused for the POTS call for data transmissions over the subscriber loop,and is responsive to the second control signal from the controlprocessor for loading ADSL data into the tone bins which are in both thepredetermined frequency band used for the POTS call and the frequencyband thereabove for data transmissions over the subscriber loop.
 2. Theapparatus of claim 1 wherein the FFT circuit of the FFT/IFFT isresponsive to the first control signal from the control processor forunloading ADSL data from the tone bins received from the subscriber loopin only the frequency band above the predetermined frequency band usedfor the POTS call for data transmission to the remote source, and isresponsive to the second control signal from the control processor forunloading ADSL data from the tone bins received from the subscriber loopwhich are in both the predetermined frequency band used for the POTScall and the frequency band thereabove for data transmission to theremote source.
 3. An apparatus for providing bidirectional AsymmetricDigital Subscriber Line (ADSL) data service and Plain Old TelephoneService (POTS) over a subscriber loop, comprising: an ADSL transceiverlocated in a local communication center for receiving ADSL data in afirst direction from a remote source and loading the received ADSL datainto predetermined tone bins for transmission over the subscriber loopto subscriber data equipment, and for receiving ADSL data in a seconddirection in the predetermined tone bins from the subscriber loop forprocessing the ADSL data for transmission to the remote source; and acontrol processor responsive to a detection of an origination of a POTScall for generating a first control signal that causes the ADSLtransceiver to load ADSL data into tone bins which are only in afrequency band above a predetermined frequency band used for a POTS callfor data transmissions over the subscriber loop, and responsive to adetection of a termination of a POTS call for generating a secondcontrol signal that causes the ADSL transceiver to load ADSL data intotone bins which are in both the predetermined frequency band used for aPOTS call and the frequency band thereabove for data transmissions overthe subscriber loop, wherein the control processor is responsive to adetection of an origination of a POTS call in the first or seconddirection over the subscriber loop for generating a third control signalwhich is transmitted as part of the ADSL data in the tone bins beingtransmitted over the subscriber loop to a subscriber modem at asubscriber end of the subscriber loop to cause the subscriber modem toload ADSL data into tone bins which are only above the predeterminedfrequency band used for the POTS call for data transmissions to the ADSLtransceiver in the local communication center, and is responsive to atermination of a POTS call on the subscriber loop for generating afourth control signal which is transmitted as part of the ADSL data inthe tone bins over the subscriber loop to a subscriber modem to causethe subscriber modem to load ADSL data into tone bins which are in boththe predetermined frequency band used for the POTS call and thefrequency band thereabove for data transmissions to the ADSL transceiverin the local communication center.
 4. The apparatus of claim 3 whereinthe subscriber modem comprises: an ADSL transceiver for receiving ADSLdata and the third or fourth control signal from the ADSL transceiver inthe local communication center and generating therefrom separate dataoutput signals and a third or fourth control output signal; and acontrol processor responsive to the third control output signal from thesubscriber modem ADSL transceiver for generating a fifth control signalthat causes the subscriber modem ADSL transceiver to (a) unload the ADSLdata received in the tone bins which are only in a frequency band abovea frequency band used for a POTS call for data transmission to asubscriber data equipment, and (b) to load ADSL data from the subscriberdata equipment into tone bins which are only in a frequency band above afrequency band used for a POTS call for data transmissions over thesubscriber loop to the ADSL transceiver in the local communicationcenter, and is responsive to the fourth output control signal receivedfrom the subscriber modem ADSL transceiver for generating a sixthcontrol signal that causes the subscriber modem ADSL transceiver to (c)unload the ADSL data received in the tone bins which are in both thefrequency band used for a POTS call and the frequency band thereabovefor data transmissions to the subscriber data equipment, and (d) loadADSL data into tone bins which are in both the frequency band used forthe POTS call transmissions and the frequency band thereabove for datatransmissions over the subscriber loop to the ADSL transceiver in thelocal communication center.
 5. An apparatus for providing bidirectionalAsymmetric Digital Subscriber Line (ADSL) data service and Plain OldTelephone Service (POTS) over a subscriber loop, comprising: an ADSLtransceiver located in a local communication center for receiving ADSLdata in a first direction from a remote source and loading the receivedADSL data into predetermined tone bins for transmission over thesubscriber loop to subscriber data equipment, and for receiving ADSLdata in a second direction in the predetermined tone bins from thesubscriber loop for processing the ADSL data for transmission to theremote source; a control processor responsive to a detection of anorigination of a POTS call for generating a first control signal thatcauses the ADSL transceiver to load ADSL data into tone bins which areonly in a frequency band above a predetermined frequency band used for aPOTS call for data transmissions over the subscriber loop, andresponsive to a detection of a termination of a POTS call for generatinga second control signal that causes the ADSL transceiver to load ADSLdata into tone bins which are in both the predetermined frequency bandused for a POTS call and the frequency band thereabove for datatransmissions over the subscriber loop, a signaling processing for voiceand signaling circuit for monitoring call states of a POTS call betweenthe remote source and the subscriber loop and for generating output callstate control signals corresponding to such call states; and a signalingsense and control circuit responsive to output control signals from thesignaling processing for voice and signaling circuit and from a POTSline coupled to the remote source for storing current POTS call states,and for generating call state control signals to the control processorcorresponding to the current POTS call states, whereby the controlprocessor generates its first or second control signal based on the callstate control signals received from the signaling sense and controlcircuit.
 6. An apparatus for providing bidirectional Asymmetric DigitalSubscriber Line (ADSL) data service and Plain Old Telephone Service(POTS) over a subscriber loop, comprising: an ADSL transceiver locatedin a local communication center for receiving ADSL data in a firstdirection from a remote source and loading the received ADSL data intopredetermined tone bins for transmission over the subscriber loop tosubscriber data equipment, and for receiving ADSL data in a seconddirection in the predetermined tone bins from the subscriber loop forprocessing the ADSL data for transmission to the remote source; acontrol processor responsive to a detection of an origination of a POTScall for generating a first control signal that causes the ADSLtransceiver to load ADSL data into tone bins which are only in afrequency band above a predetermined frequency band used for a POTS callfor data transmissions over the subscriber loop, and responsive to adetection of a termination of a POTS call for generating a secondcontrol signal that causes the ADSL transceiver to load ADSL data intotone bins which are in both the predetermined frequency band used for aPOTS call and the frequency band thereabove for data transmissions overthe subscriber loop; and a second ADSL transceiver located in a localcommunication center for receiving ADSL data in a first direction from aremote source and loading the received ADSL data into predetermined tonebins for data transmissions over a second subscriber loop to anassociated second subscriber data equipment, and for receiving ADSL datain a second direction in the predetermined tone bins from the secondsubscriber loop for processing the ADSL data for transmission to theremote source, and wherein the control processor is responsive to adetection of an origination of a POTS call on the second subscriber loopfor generating a first control signal that causes the second ADSLtransceiver to load ADSL data into tone bins which are only in afrequency band that is above a predetermined frequency band used for aPOTS call for data transmissions over the second subscriber loop, and isresponsive to a detection of a termination of a POTS call on the secondsubscriber loop for generating a second control signal that causes thesecond ADSL transceiver to load ADSL data into tone bins which are inboth the predetermined frequency band used for a POTS call and thefrequency band thereabove for data transmissions over the secondsubscriber loop.
 7. The apparatus of claim 6 wherein the controlprocessor is responsive to a detection of an origination of a POTS callin the first or second direction over the second subscriber loop forgenerating a third control signal which is transmitted as part of theADSL data in the tone bins being transmitted over the second subscriberloop to a second subscriber modem at a subscriber end of the secondsubscriber loop to cause the second subscriber modem to load ADSL datainto tone bins which are only above the predetermined frequency bandused for the POTS call for data transmissions to the second ADSLtransceiver in the local communication center, and is responsive to adetection of a termination of a POTS call on the second subscriber loopfor generating a fourth control signal which is transmitted as part ofthe ADSL data in the tone bins over the second subscriber loop to thesecond subscriber modem to cause the second subscriber modem to loadADSL data into tone bins which are in both the predetermined frequencyband used for the POTS call and the frequency band thereabove for datatransmissions to the second ADSL transceiver in the local communicationcenter.
 8. The apparatus of claim 7 wherein the second subscriber modemcomprises: an ADSL transceiver for receiving both ADSL data signals andthe third or fourth control signal from the second ADSL transceiver inthe local communication center and generating therefrom separate dataoutput signals and the third or fourth control output signal; and acontrol processor responsive to the third control output signal from thesecond subscriber modem ADSL transceiver for generating a fifth controlsignal that causes the second subscriber modem ADSL transceiver to (a)unload the ADSL data received in the tone bins which are only in afrequency band above a frequency band used for a POTS call for datatransmissions to the second subscriber data equipment, and (b) to loadADSL data from the second subscriber data equipment into tone bins whichare only in a frequency band above a frequency band used for a POTS callfor ADSL data transmissions over the second subscriber loop to thesecond ADSL transceiver in the local communication center, and isresponsive to the fourth output control signal received from the secondsubscriber modem ADSL transceiver for generating a sixth control signalthat causes the second subscriber modem ADSL transceiver to (c) unloadthe ADSL data received in the tone bins which are in both the frequencyband used for a POTS call and the frequency band thereabove for datatransmissions to the second subscriber data equipment, and (d) load ADSLdata from the subscriber data equipment into tone bins which are in boththe frequency band normally used for the POTS call transmissions and thefrequency band thereabove for ADSL data transmissions over the secondsubscriber loop to the second ADSL transceiver in the localcommunication center.
 9. An apparatus for providing bidirectionalAsymmetric Digital Subscriber Line (ADSL) data service and Plain OldTelephone Service (POTS) over a subscriber loop, comprising: an ADSLtransceiver located in a local communication center for receiving ADSLdata in a first direction from a remote source and loading the receivedADSL data into predetermined tone bins for transmission over thesubscriber loop to subscriber data equipment, and for receiving ADSLdata in a second direction in the predetermined tone bins from thesubscriber loop for processing the ADSL data for transmission to theremote source; a control processor responsive to a detection of anorigination of a POTS call for generating a first control signal thatcauses the ADSL transceiver to load ADSL data into tone bins which areonly in a frequency band above a predetermined frequency band used for aPOTS call for data transmissions over the subscriber loop, andresponsive to a detection of a termination of a POTS call for generatinga second control signal that causes the ADSL transceiver to load ADSLdata into tone bins which are in both the predetermined frequency bandused for a POTS call and the frequency band thereabove for datatransmissions over the subscriber loop; an ADSL transceiver located at asubscriber location for receiving ADSL data in a first direction overthe subscriber loop from the ADSL transceiver in the local communicationcenter and unloading the received ADSL data from predetermined tone binsfor transmission over the subscriber loop to subscriber data equipment,and for receiving ADSL data in a second direction from the subscriberdata equipment and loading the ADSL data into predetermined tone binsfor transmission over the subscriber loop to the ADSL transceiver in thelocal communication center; and a control processor located at thesubscriber location responsive to a detection of an origination of aPOTS call for generating a first control signal that causes the ADSLtransceiver to load ADSL data into tone bins which are only in afrequency band above a predetermined frequency band used for a POTS callfor data transmission over the subscriber loop to the ADSL transceiverin the local communication center, and responsive to a detection of atermination of a POTS call for generating a second control signal thatcauses the ADSL transceiver to load ADSL data into tone bins which arein both the predetermined frequency band used for a POTS call and thefrequency band thereabove for data transmissions over the subscriberloop to the ADSL transceiver in the local communication center.
 10. Theapparatus of claim 9 further comprising: a ringing and DC level detectorfor detecting either one of a ringing signal on the subscriber loop or aDC level change on the subscriber loop indicating the initiation of POTScall for generating a first output control signal, and for detecting atermination of a POTS call at the subscriber location, for generating asecond control output signal; and the control processor is responsive tothe first control output signal from the ringing and DC level detectorfor generating the first control signal to the ADSL transceiver at asubscriber location, and is responsive to the second control outputsignal from the ringing and DC level detector for generating the secondcontrol signal to the ADSL transceiver at a subscriber location.
 11. Anapparatus for implementing bidirectional Asymmetric Digital SubscriberLine (ADSL) data service and Plain Old Telephone Service (POTS) over asubscriber loop comprising: an integrated line circuit (ILC) located ina local communication center comprising: detecting and processingcircuitry for detecting an origination or termination of a POTS calldirected to or from a subscriber coupled to the subscriber loop, and forbidirectionally processing the POTS call for transmission between aremote source and the subscriber loop; an ADSL transceiver for receivingADSL data in a first direction from a remote source and loading thereceived ADSL data into predetermined tone bins for data transmissionsover the subscriber loop to subscriber data equipment, and for receivingADSL data in a second direction in the predetermined tone bins from thesubscriber loop for processing the ADSL data for data transmission tothe remote source; and a control processor responsive to a detection ofan origination of a POTS call by the detecting and processing circuitryfor generating a first control signal that causes the ADSL transceiverto load ADSL data into tone bins which are only in a frequency bandabove a predetermined frequency band used for a POTS call for ADSL datatransmissions over the subscriber loop, and responsive to a detection ofa termination of a POTS call by the detecting and processing circuitryfor generating a second control signal that causes the ADSL transceiverto load ADSL data into tone bins which are in both the predeterminedfrequency band used for a POTS call and the frequency band thereabovefor ADSL data transmissions over the subscriber loop, wherein the ADSLtransceiver comprises a Fast Fourier Transform/Inverse Fast FourierTransform (FFT/IFFT) circuit wherein the IFFT circuit is responsive tothe first control signal from the control processor for loading ADSLdata into the tone bins in the frequency band above the predeterminedfrequency band used for the POTS call for ADSL data transmissions overthe subscriber loop, and is responsive to the second control signal fromthe control processor for loading ADSL data into the tone bins which arein both the predetermined frequency band used for the POTS call and thefrequency band thereabove for ADSL data transmissions over thesubscriber loop.
 12. The apparatus of claim 11 wherein the FFT circuitof the FFT/IFFT circuit is responsive to the first control signal fromthe control processor for unloading ADSL data from the tone binsreceived from the subscriber loop in only the frequency band above thepredetermined frequency band used for the POTS call for datatransmissions to the remote source, and is responsive to the secondcontrol signal from the control processor for unloading ADSL data fromthe tone bins received from the subscriber loop which are in both thepredetermined frequency band used for the POTS call and the frequencyband thereabove for data transmissions to the remote source.
 13. Anapparatus for implementing bidirectional Asymmetric Digital SubscriberLine (ADSL) data service and Plain Old Telephone Service (POTS) over asubscriber loop comprising: an integrated line circuit (ILC) located ina local communication center comprising: detecting and processingcircuitry for detecting an origination or termination of a POTS calldirected to or from a subscriber coupled to the subscriber loop, and forbidirectionally processing the POTS call for transmission between aremote source and the subscriber loop; an ADSL transceiver for receivingADSL data in a first direction from a remote source and loading thereceived ADSL data into predetermined tone bins for data transmissionsover the subscriber loop to subscriber data equipment, and for receivingADSL data in a second direction in the predetermined tone bins from thesubscriber loop for processing the ADSL data for data transmission tothe remote source; and a control processor responsive to a detection ofan origination of a POTS call by the detecting and processing circuitryfor generating a first control signal that causes the ADSL transceiverto load ADSL data into tone bins which are only in a frequency bandabove a predetermined frequency band used for a POTS call for ADSL datatransmissions over the subscriber loop, and responsive to a detection ofa termination of a POTS call by the detecting and processing circuitryfor generating a second control signal that causes the ADSL transceiverto load ADSL data into tone bins which are in both the predeterminedfrequency band used for a POTS call and the frequency band thereabovefor ADSL data transmissions over the subscriber loop, wherein thecontrol processor is responsive to an origination of a POTS call in thefirst or second direction over the subscriber loop for generating athird control signal which is transmitted as part of the ADSL data inthe tone bins being transmitted over the subscriber loop to a subscribermodem at a subscriber end of the subscriber loop to cause the subscribermodem to load ADSL data into tone bins which are in the frequency bandabove the predetermined frequency band used for the POTS call for ADSLdata transmissions over the subscriber loop, and is responsive to atermination of a POTS call on the subscriber loop for generating afourth control signal which is transmitted as part of the ADSL data inthe tone bins over the subscriber loop to the subscriber modem to causethe subscriber modem to load ADSL data into tone bins which are in boththe predetermined frequency band used for the POTS call and thefrequency band thereabove for ADSL data transmissions over thesubscriber loop.
 14. The apparatus of claim 13 wherein the subscribermodem comprises: an ADSL transceiver for receiving both ADSL datasignals and the third or fourth control signal from the ADSL transceiverin the local communication center and generating therefrom separate dataoutput signals and third or fourth control output signals; and a controlprocessor responsive to the third control output signal from thesubscriber modem ADSL transceiver for generating a fifth control signalthat causes the subscriber modem ADSL transceiver to (a) unload the ADSLdata received in the tone bins which are only in a frequency band abovea frequency band used for a POTS call for data transmissions to asubscriber data equipment, and (b) to load ADSL data from the subscriberdata equipment into tone bins which are only in a frequency band above afrequency band used for a POTS call for ADSL data transmissions over thesubscriber loop to the ADSL transceiver in the local communicationcenter, and is responsive to the fourth output control signal receivedfrom the subscriber modem ADSL transceiver for generating a sixthcontrol signal that causes the subscriber modem ADSL transceiver to (c)unload the ADSL data received in the tone bins which are in both thefrequency band for a POTS call and the frequency band thereabove fordata transmissions to the subscriber data equipment, and (d) load ADSLdata into tone bins which are in both the frequency band normally usedfor the POTS call and the frequency band thereabove for ADSL datatransmissions over the subscriber loop to the ADSL transceiver in thelocal communication center.
 15. An apparatus for implementingbidirectional Asymmetric Digital Subscriber Line (ADSL) data service andPlain Old Telephone Service (POTS) over a subscriber loop comprising: anintegrated line circuit (ILC) located in a local communication centercomprising: detecting and processing circuitry for detecting anorigination or termination of a POTS call directed to or from asubscriber coupled to the subscriber loop, and for bidirectionallyprocessing the POTS call for transmission between a remote source andthe subscriber loop; an ADSL transceiver for receiving ADSL data in afirst direction from a remote source and loading the received ADSL datainto predetermined tone bins for data transmissions over the subscriberloop to subscriber data equipment, and for receiving ADSL data in asecond direction in the predetermined tone bins from the subscriber loopfor processing the ADSL data for data transmission to the remote source;and a control processor responsive to a detection of an origination of aPOTS call by the detecting and processing circuitry for generating afirst control signal that causes the ADSL transceiver to load ADSL datainto tone bins which are only in a frequency band above a predeterminedfrequency band used for a POTS call for ADSL data transmissions over thesubscriber loop, and responsive to a detection of a termination of aPOTS call by the detecting and processing circuitry for generating asecond control signal that causes the ADSL transceiver to load ADSL datainto tone bins which are in both the predetermined frequency band usedfor a POTS call and the frequency band thereabove for ADSL datatransmissions over the subscriber loop, wherein the detecting andprocessing circuitry comprises: a signaling processing for voice andsignaling circuit for monitoring call states of a POTS call between theremote source and the subscriber loop and for generating call stateoutput control signals corresponding to such call states; and asignaling sense and control circuit responsive to call state outputcontrol signals from the signaling processing for voice and signalingcircuit and call state signals received from a POTS line coupled to theremote source for storing current POTS call states, for generatingcontrol signals to the control processor corresponding to the currentPOTS call states, whereby the control processor generates its first orsecond control signal based on the control signals from the signalingsense and control circuit.
 16. An apparatus for implementingbidirectional Asymmetric Digital Subscriber Line (ADSL) data service andPlain Old Telephone Service (POTS) over a subscriber loop comprising: anintegrated line circuit (ILC) located in a local communication centercomprising: detecting and processing circuitry for detecting anorigination or termination of a POTS call directed to or from asubscriber coupled to the subscriber loop, and for bidirectionallyprocessing the POTS call for transmission between a remote source andthe subscriber loop; an ADSL transceiver for receiving ADSL data in afirst direction from a remote source and loading the received ADSL datainto predetermined tone bins for data transmissions over the subscriberloop to subscriber data equipment, and for receiving ADSL data in asecond direction in the predetermined tone bins from the subscriber loopfor processing the ADSL data for data transmission to the remote source;a control processor responsive to a detection of an origination of aPOTS call by the detecting and processing circuitry for generating afirst control signal that causes the ADSL transceiver to load ADSL datainto tone bins which are only in a frequency band above a predeterminedfrequency band used for a POTS call for ADSL data transmissions over thesubscriber loop, and responsive to a detection of a termination of aPOTS call by the detecting and processing circuitry for generating asecond control signal that causes the ADSL transceiver to load ADSL datainto tone bins which are in both the predetermined frequency band usedfor a POTS call and the frequency band thereabove for ADSL datatransmissions over the subscriber loop; and a second ADSL transceiverlocated in the local communication center for receiving ADSL data in afirst direction from the remote source and loading the received ADSLdata into predetermined tone bins for ADSL data transmissions over asecond subscriber loop to an associated subscriber data equipment, andfor receiving ADSL data in a second direction in the predetermined tonebins from the second subscriber loop for processing the ADSL data fordata transmissions to the remote source, wherein the control processoris responsive to a detection of an origination of a POTS call on thesecond subscriber loop for generating a first control signal that causesthe second ADSL transceiver to load ADSL data into tone bins which areonly in a frequency band above a predetermined frequency band used for aPOTS call for ADSL data transmissions over the second subscriber loop,and is responsive to a detection of a termination of a POTS call on thesecond subscriber loop for generating a second control signal thatcauses the second ADSL transceiver to load ADSL data into tone binswhich are in both the predetermined frequency band used for a POTS calland the frequency band thereabove for ADSL data transmissions over thesecond subscriber loop.
 17. The apparatus of claim 16 wherein thecontrol processor is responsive to an origination of a POTS call in thefirst or second direction over the second subscriber loop for generatinga third control signal which is transmitted as part of the ADSL data inthe tone bins being transmitted over the second subscriber loop to asecond subscriber modem at the subscriber end of the second subscriberloop to cause the second subscriber modem to load ADSL data into tonebins which are in a frequency band above the predetermined frequencyband used for the POTS call for ADSL data transmissions over the secondsubscriber loop to the second ADSL transceiver in the localcommunication center, and is responsive to a termination of a POTS callon the second subscriber loop for generating a fourth control signalwhich is transmitted as part of the ADSL data in the tone bins over thesecond subscriber loop to the second subscriber modem to cause thesecond subscriber modem to load ADSL data into tone bins which are inboth the predetermined frequency band used for the POTS call and thefrequency band thereabove for ADSL data transmissions over the secondsubscriber loop to the second ADSL transceiver in the localcommunication center.
 18. The apparatus of claim 17 wherein the secondsubscriber modem comprises: an ADSL transceiver for receiving both ADSLdata signals and the third or fourth control signal from the second ADSLtransceiver in the local communication center and for generatingseparate data output signals and the third or fourth control outputsignal; and a control processor responsive to the third control outputsignal from the second subscriber modem ADSL transceiver for generatinga fifth control signal that causes the second subscriber modem ADSLtransceiver to (a) unload the ADSL data received in the tone bins whichare only in the frequency band above the predetermined frequency bandused for a POTS call for data transmissions to the second subscriberdata equipment, and (b) to load ADSL data from the second subscriberdata equipment into tone bins which are only in the frequency band abovethe frequency band used for a POTS call for ADSL data transmissions overthe second subscriber loop to the second ADSL transceiver in the localcommunication center, and is responsive to the fourth output controlsignal received from the second subscriber modem ADSL transceiver forgenerating a sixth control signal that causes the second subscribermodem ADSL transceiver to (c) unload the ADSL data received in the tonebins which are in both the frequency band for a POTS call and thefrequency band thereabove for data transmissions to the secondsubscriber data equipment, and (d) load ADSL data into tone bins whichare in both the frequency band normally used for the POTS calltransmissions and the frequency band thereabove for ADSL datatransmissions over the second subscriber loop to the second ADSLtransceiver in the local communication center.
 19. An apparatus forimplementing bidirectional Asymmetric Digital Subscriber Line (ADSL)data service and Plain Old Telephone Service (POTS) over a subscriberloop comprising: an integrated line circuit (ILC) located in a localcommunication center comprising: detecting and processing circuitry fordetecting an origination or termination of a POTS call directed to orfrom a subscriber coupled to the subscriber loop, and forbidirectionally processing the POTS call for transmission between aremote source and the subscriber loop; an ADSL transceiver for receivingADSL data in a first direction from a remote source and loading thereceived ADSL data into predetermined tone bins for data transmissionsover the subscriber loop to subscriber data equipment, and for receivingADSL data in a second direction in the predetermined tone bins from thesubscriber loop for processing the ADSL data for data transmission tothe remote source; a control processor responsive to a detection of anorigination of a POTS call by the detecting and processing circuitry forgenerating a first control signal that causes the ADSL transceiver toload ADSL data into tone bins which are only in a frequency band above apredetermined frequency band used for a POTS call for ADSL datatransmissions over the subscriber loop, and responsive to a detection ofa termination of a POTS call by the detecting and processing circuitryfor generating a second control signal that causes the ADSL transceiverto load ADSL data into tone bins which are in both the predeterminedfrequency band used for a POTS call and the frequency band thereabovefor ADSL data transmissions over the subscriber loop; an ADSLtransceiver located at a subscriber location for receiving ADSL data ina first direction over the subscriber loop from the ADSL transceiver inthe local communication center and unloading the received ADSL data frompredetermined tone bins for transmission over the subscriber loop tosubscriber data equipment, and for receiving ADSL data in a seconddirection from the subscriber data equipment and loading the ADSL datainto predetermined tone bins for transmission over the subscriber loopto the ADSL transceiver in the local communication center; and a controlprocessor located at the subscriber location responsive to a detectionof an origination of a POTS call for generating a first control signalthat causes the ADSL transceiver to load ADSL data into tone bins whichare only in a frequency band above a predetermined frequency band usedfor a POTS call for data transmissions over the subscriber loop to theADSL transceiver in the local communication center, and responsive to adetection of a termination of a POTS call for generating a secondcontrol signal that causes the ADSL transceiver to load ADSL data intotone bins which are in both the predetermined frequency band used for aPOTS call and the frequency band thereabove for data transmissions overthe subscriber loop to the ADSL transceiver in the local communicationcenter.
 20. The apparatus of claim 19 further comprising: a ringing andDC level detector for detecting either one of a ringing signal on thesubscriber loop or a DC level change on the subscriber loop indicatingthe initiation of POTS call for generating a first output controlsignal, and for detecting a termination of a POTS call at the subscriberlocation, for generating a second control output signal; and the controlprocessor is responsive to the first control output signal from theringing and DC level detector for generating the first control signal tothe ADSL transceiver at a subscriber location, and is responsive to thesecond control output signal from the ringing and DC level detector forgenerating the second control signal to the ADSL transceiver at asubscriber location.